Candida Non-albicans and Non-auris Causing Invasive Candidiasis in a Fourth-Level Hospital in Colombia: Epidemiology, Antifungal Susceptibility, and Genetic Diversity

Increasingly common and associated with healthcare settings, Candida infections are very important, since some species of this genus can develop antifungal resistance. We contribute data on the epidemiology, antifungal susceptibility, and genetic diversity of Candida non-albicans and non-auris affecting critically ill patients in a fourth-level hospital in Colombia. Ninety-seven isolates causing invasive infections, identified by conventional methods over 18 months, were studied. Data from patients affected by these yeasts, including sex, age, comorbidities, treatment, and outcome, were analysed. The antifungal susceptibility of the isolates was determined, and the ribosomal DNA was sequenced. Candida parapsilosis, Candida tropicalis, Candida glabrata, Candida dubliniensis, and Candida guilliermondii caused 48.5% of all cases of invasive candidiasis. The species were mainly recovered from blood (50%). Patients were mostly men (53.4%), between 18 days and 93 years old, hospitalized in the ICU (70.7%). Overall mortality was 46.6%, but patients in the ICU, using antibiotics, with diabetes mellitus, or with C. glabrata infections were more likely to die. Resistant isolates were identified in C. parapsilosis, C. tropicalis, and C. glabrata. This study provides epidemiological data for the surveillance of emerging Candida species, highlighting their clinical impact, as well as the emergence of antifungal resistance and clonal dispersal.

Pore-forming peptide C14R exhibits potent antifungal activity against clinical isolates of Candida albicans and Candida auris

Introduction

Invasive candidiasis is a global public health problem as it poses a significant threat in hospital-settings. The aim of this study was to evaluate C14R, an analog derived from peptide BP100, as a potential antimicrobial peptide against the prevalent opportunistic yeast Candida albicans and the emergent multidrug-resistant yeast Candida auris.

Methods

Antifungal susceptibility testing of C14R against 99 C. albicans and 105 C. auris clinical isolates from Colombia, was determined by broth microdilution. Fluconazole was used as a control antifungal. The synergy between C14R and fluconazole was assessed in resistant isolates. Assays against fungal biofilm and growth curves were also carried out. Morphological alterations of yeast cell surface were evaluated by scanning electron microscopy. A permeability assay verified the pore-forming ability of C14R.

Results

C. albicans and C. auris isolates had a geometric mean MIC against C14R of 4.42 µg/ml and 5.34 µg/ml, respectively. Notably, none of the isolates of any species exhibited growth at the highest evaluated peptide concentration (200 µg/ml). Synergistic effects were observed when combining the peptide and fluconazole. C14R affects biofilm and growth of C. albicans and C. auris. Cell membrane disruptions were observed in both species after treatment with the peptide. It was confirmed that C14R form pores in C. albicans' membrane.

Discussion

C14R has a potent antifungal activity against a large set of clinical isolates of both C. albicans and C. auris, showing its capacity to disrupt Candida membranes. This antifungal activity remains consistent across isolates regardless of their clinical source. Furthermore, the absence of correlation between MICs to C14R and resistance to fluconazole indicates the peptide's potential effectiveness against fluconazole-resistant strains. Our results suggest the potential of C14R, a pore-forming peptide, as a treatment option for fungal infections, such as invasive candidiasis, including fluconazole and amphotericin B -resistant strains.

Multi-locus sequence typing and phylogenetics of Cryptococcus neoformans AD hybrids

Hybrid AD strains of the human pathogenic Cryptococcus neoformans species complex have been reported from many parts of the world. However, their origin, diversity, and evolution are incompletely understood. In this study, we analyzed 102 AD hybrid strains representing 21 countries on five continents. For each strain, we obtained its mating type and its allelic sequences at each of the seven loci that have been used for genotyping haploid serotypes A and D strains of the species complex by the Cryptococcus research community. Our results showed that most AD hybrids exhibited loss of heterozygosity at one or more of the seven analyzed loci. Phylogenetic and population genetic analyses of the allelic sequences revealed multiple origins of the hybrids within each continent, dating back to one million years ago in Africa and up to the present in other continents. We found evidence for clonal reproduction and long-distance dispersal of these hybrids in nature. Comparisons with the global haploid serotypes A and D strains identified new alleles and new haploid multi-locus genotypes in AD hybrids, consistent with the presence of yet-to-be discovered genetic diversity in haploid populations of this species complex in nature. Together, our results indicate that AD hybrids can be effectively genotyped using the same multi-locus sequencing type approach as that established for serotypes A and D strains. Our comparisons of the AD hybrids among each other as well as with the global haploid serotypes A and D strains revealed novel genetic diversity as well as evidence for multiple origins and dynamic evolution of these hybrids in nature.

Autoantibodies neutralizing GM-CSF in HIV-negative Colombian patients infected with Cryptococcus gattii and C. neoformans

Background

Cryptococcosis is a life-threatening disease caused by Cryptococcus neoformans or C. gattii. Autoantibodies (auto-Abs) neutralizing granulocyte-macrophage colony-stimulating factor (GM-CSF) in otherwise healthy adults with cryptococcal meningitis have been described since 2013. We searched for neutralizing auto-Abs in sera from Colombian patients with non-HIV related cryptococcosis in a retrospective national cohort collected from 1997 to 2016.

Methods

We reviewed clinical and laboratory records and assessed the presence of neutralizing auto-Abs in 30 HIV (-) adults presenting cryptococcosis (13 by C. gattii, and 17 by C. neoformans).

Results

We detected auto-Abs neutralizing GM-CSF in the plasma of 9 out of 13 (69%) patients infected with C. gattii and 1 out of 17 (6%) patients with C. neoformans.

Conclusions

We report ten Colombian patients with cryptococcosis due to auto-Abs neutralizing GM-CSF. Nine of the ten patients were infected with C. gattii, and only one with C. neoformans.

Therapeutic Use of the Antimicrobial Peptide PNR20 to Resolve Disseminated Candidiasis in a Murine Model

Invasive fungal infections (IFIs) caused by Candida species are an emerging threat globally, given that patients at-risk and antifungal resistance are increasing. Antimicrobial peptides (AMPs) have shown good therapeutic capacity against different multidrug-resistant (MDR) microorganisms. This study evaluated the activity of the synthetic peptide, PNR20, against Candida albicans ATCC 10231 and a MDR Colombian clinical isolate of Candida auris. Perturbation of yeast cell surface was evaluated using scanning electron microscopy. Cell viability of Vero cells was determined to assess peptide toxicity. Additionally, survival, fungal burden, and histopathology of BALB/c mice infected intravenously with each Candida species and treated with PNR20 were analyzed. Morphological alterations were identified in both species, demonstrating the antifungal effect of PNR20. In vitro, Vero cells' viability was not affected by PNR20. All mice infected with either C. albicans or C. auris and treated with PNR20 survived and had a significant reduction in the fungal burden in the kidney compared to the control group. The histopathological analysis in mice infected and treated with PNR20 showed more preserved tissues, without the presence of yeast, compared to the control groups. This work shows that the utilization of PNR20 is a promising therapeutic alternative against disseminated candidiasis.

Reduced Susceptibility to Azoles in Cryptococcus gattii Correlates with the Substitution R258L in a Substrate Recognition Site of the Lanosterol 14-α-Demethylase

Cryptococcus neoformans and Cryptococcus gattii cause cryptococcosis, a life-threatening fungal infection affecting mostly immunocompromised patients. In fact, cryptococcal meningitis accounts for about 19% of AIDS-related deaths in the world. Because of long-term azole therapies to treat this mycosis, resistance to fluconazole leading to treatment failure and poor prognosis has long been reported for both fungal species. Among the mechanisms implicated in resistance to azoles, mutations in the ERG11 gene, encoding the azole target enzyme lanosterol 14-α-demethylase, have been described. This study aimed to establish the amino acid composition of ERG11 of Colombian clinical isolates of C. neoformans and C. gattii and to correlate any possible substitution with the in vitro susceptibility profile of the isolates to fluconazole, voriconazole, and itraconazole. Antifungal susceptibility testing results showed that C. gattii isolates are less susceptible to azoles than C. neoformans isolates, which could correlate with differences in the amino acid composition and structure of ERG11 of each species. In addition, in a C. gattii isolate with high MICs for fluconazole (64 μg/mL) and voriconazole (1 μg/mL), a G973T mutation resulting in the substitution R258L, located in substrate recognition site 3 of ERG11, was identified. This finding suggests the association of the newly reported substitution with the azole resistance phenotype in C. gattii. Further investigations are needed to determine the exact role that R258L plays in the decreased susceptibility to fluconazole and voriconazole, as well as to determine the participation of additional mechanisms of resistance to azole drugs. IMPORTANCE The fungal species Cryptococcus neoformans and C. gattii are human pathogens for which drug resistance or other treatment and management challenges exist. Here, we report differential susceptibility to azoles among both species, with some isolates displaying resistant phenotypes. Azoles are among the most commonly used drugs to treat cryptococcal infections. Our findings underscore the necessity of testing antifungal susceptibility in the clinical setting in order to assist patient management and beneficial outcomes. In addition, we report an amino acid change in the sequence of the target protein of azoles, which suggests that this change might be implicated in resistance to these drugs. Identifying and understanding possible mechanisms that affect drug affinity will eventually aid the design of new drugs that overcome the global growing concern of antifungal resistance.

In Vitro Antifungal Activity of Three Synthetic Peptides against Candida auris and Other Candida Species of Medical Importance

Candidiasis is an opportunistic infection affecting immunosuppressed and hospitalized patients, with mortality rates approaching 40% in Colombia. The growing pharmacological resistance of Candida species and the emergence of multidrug-resistant Candida auris are major public health problems. Therefore, different antimicrobial peptides (AMPs) are being investigated as therapeutic alternatives to control candidiasis effectively and safely. This work aimed to evaluate the in vitro antifungal activity of three synthetic AMPs, PNR20, PNR20-1, and 35409, against ATCC reference strains of Candida albicans, Candida glabrata, Candida parapsilosis, Candida krusei, and Candida tropicalis, and clinical isolates of C. auris. Antifungal susceptibility testing, determined by broth microdilution, showed that the AMPs have antifungal activity against planktonic cells of all Candida species evaluated. In C. auris and C. albicans, the peptides had an effect on biofilm formation and cell viability, as determined by the XTT assay and flow cytometry, respectively. Also, morphological alterations in the membrane and at the intracellular level of these species were induced by the peptides, as observed by transmission electron microscopy. In vitro, the AMPs had no cytotoxicity against L929 murine fibroblasts. Our results showed that the evaluated AMPs are potential therapeutic alternatives against the most important Candida species in Colombia and the world.

Rare Yeasts in Latin America: Uncommon Yet Meaningful

Systemic infections caused by rare yeasts are increasing given the rise in immunocompromised or seriously ill patients. Even though globally, the clinical significance of these emerging opportunistic yeasts is increasingly being recognized, less is known about the epidemiology of rare yeasts in Latin America. This review collects, analyzes, and contributes demographic and clinical data from 495 cases of infection caused by rare yeasts in the region. Among all cases, 32 species of rare yeasts, distributed in 12 genera, have been reported in 8 Latin American countries, with Trichosporon asahii (49.5%), Rhodotorula mucilaginosa (11.1%), and Saccharomyces cerevisiae (7.8%) the most common species found. Patients were mostly male (58.3%), from neonates to 84 years of age. Statistically, surgery and antibiotic use were associated with higher rates of Trichosporon infections, while central venous catheter, leukemia, and cancer were associated with higher rates of Rhodotorula infections. From all cases, fungemia was the predominant diagnosis (50.3%). Patients were mostly treated with amphotericin B (58.7%). Crude mortality was 40.8%, with a higher risk of death from fungemia and T. asahii infections. Culture was the main diagnostic methodology. Antifungal resistance to one or more drugs was reported in various species of rare yeasts.

Cm-p5 Peptide Dimers Inhibit Biofilms of Candida albicans Clinical Isolates, C. parapsilosis and Fluconazole-Resistant Mutants of C. auris

Antimicrobial peptides (AMPs) represent a promising class of therapeutic biomolecules that show antimicrobial activity against a broad range of microorganisms, including life-threatening pathogens. In contrast to classic AMPs with membrane-disrupting activities, new peptides with a specific anti-biofilm effect are gaining in importance since biofilms could be the most important way of life, especially for pathogens, as the interaction with host tissues is crucial for the full development of their virulence in the event of infection. Therefore, in a previous study, two synthetic dimeric derivatives (parallel Dimer 1 and antiparallel Dimer 2) of the AMP Cm-p5 showed specific inhibition of the formation of Candida auris biofilms. Here we show that these derivatives are also dose-dependently effective against de novo biofilms that are formed by the widespread pathogenic yeasts C. albicans and C. parapsilosis. Moreover, the activity of the peptides was demonstrated even against two fluconazole-resistant strains of C. auris.

Antimicrobial Peptides: Avant-Garde Antifungal Agents to Fight against Medically Important Candida Species

Expanding the antifungal drug arsenal for treating Candida infections is crucial in this era of the rising life expectancy of patients with immunosuppression and comorbidities. Infections caused by Candida species are on the rise, including those caused by multidrug-resistant strains or species, and the list of antifungals approved for the treatment of these infections is still limited. Antimicrobial peptides (AMPs) are short cationic polypeptides whose antimicrobial activity is under intense investigation. In this review, we present a comprehensive summary of the AMPs with anti-Candida activity that have undergone successful preclinical or clinical trials. Their source, mode of action, and animal model of infection (or clinical trial) are presented. In addition, as some of these AMPs have been tested in combination therapy, the advantages of this approach, as well as the studied cases that have used AMPs and other drugs concomitantly to fight Candida infections, are described.

Genotypic Diversity and Antifungal Susceptibility of Clinical Isolates of Cryptococcus Gattii Species Complex from Argentina

The aim of this study was to determine the genotypic diversity of 22 Cryptococcus gattii species complex clinical isolates from Argentina and to place these genotypes within the diversity of clinical, veterinary and environmental isolates from Latin America. Mating type and antifungal susceptibility of the isolates were also determined. By URA5-RFLP, nine isolates were identified as molecular type VGI, 10 as VGII, one as VGIII and two as VGIV. Multilocus sequence typing (MSLT), following the International Society for Human and Animal Mycology (ISHAM) consensus MLST scheme, was used to determine the genotypic diversity. Our results suggest that, in Argentina, VGI isolates have low genetic diversity, while VGII isolates have high genetic diversity. Both isolates identified as VGIV by URA5-RFLP were genotyped by MLST as belonging to the currently named VGVI clade. From all isolates, eight sequence types (STs) were unique for Argentina, while five STs have been reported already in other countries, being of high interest the genotypes ST20 and ST7 since they belong to the subtypes VGIIa and VGIIb, respectively, which are associated with hypervirulent strains responsible for outbreaks in North America. To note, geographical analysis showed that some genotypes may be associated with some regions in Argentina. Most isolates were MATα, but we are reporting one isolate MATa for the first time in the country. Antifungal susceptibility tests showed that itraconazole, voriconazole and posaconazole had high activity against all isolates, while amphotericin B, fluconazole and 5-fluorocytosine were the least active drugs against all studied isolates.

Cryptococcus neoformans Causing Meningoencephalitis in Adults and a Child from Lima, Peru: Genotypic Diversity and Antifungal Susceptibility

Cryptococcosis, caused predominantly by Cryptococcus neoformans, is a potentially fatal, opportunistic infection that commonly affects the central nervous system of immunocompromised patients. Globally, this mycosis is responsible for almost 20% of AIDS-related deaths, and in countries like Peru, its incidence remains high, mostly due to the annual increase in new cases of HIV infection. This study aimed to establish the genotypic diversity and antifungal susceptibility of C. neoformans isolates causing meningoencephalitis in 25 adults and a 9-year-old girl with HIV and other risk factors from Lima, Peru. To identify the genotype of the isolates, multilocus sequence typing was applied, and to establish the susceptibility of the isolates to six antifungals, a YeastOne® broth microdilution was used. From the isolates, 19 were identified as molecular type VNI, and seven as VNII, grouped in eight and three sequence types, respectively, which shows that the studied population was highly diverse. Most isolates were susceptible to all antifungals tested. However, VNI isolates were less susceptible to fluconazole, itraconazole and voriconazole than VNII isolates (p < 0.05). This study contributes data on the molecular epidemiology and the antifungal susceptibility profile of the most common etiological agent of cryptococcosis, highlighting a pediatric case, something which is rare among cryptococcal infection.

S8.5d Cryptococcus neoformans and Cryptococcus gattii clinical isolates from Colombia develop heteroresistance to fluconazole at high concentrations

S8.5 Genotyping of Cryptococcus neoformans and C. gattii, September 23, 2022, 3:00 PM - 4:30 PM

 

Introduction

Cryptococcosis is a worldwide mycosis caused by Cryptococcus neoformans and Cryptococcus gattii. Although resistance to antifungals is infrequent, isolates with decreased susceptibility to fluconazole have been reported globally, including Colombia, which may be due to 1) heteroresistance, defined as the ability to adapt to increasing concentrations of this azolic antifungal, and 2) point mutations in the EGR11 gene encoding the fluconazole target enzyme, lanosterol 14-α-demethylase.

Objective

To determine the development of heteroresistance to fluconazole in C. neoformans and C. gattii clinical isolates from Colombia and to amplify and sequence the ERG11 gene of the isolates to seek for mutations that might characterize resistant or heteroresistant phenotypes.

Methods

The minimum inhibitory concentration (MIC) to fluconazole was determined in 31 and 24 isolates of C. neoformans and C. gattii, respectively, using broth microdilution. Heteroresistance was evaluated by plating each isolate on YPD agar that contained fluconazole at concentrations equal to the MIC of each isolate. Heteroresistant colonies were then replated at increasing concentrations of fluconazole, as high as 128 μg/ml.

Results

All isolates were susceptible to fluconazole with MICs of 1 μg/ml (n = 3), 2 μg/ml (n = 6), 4 μg/ml (n = 17), 8 μg/ml (n = 23), 16 μg/ml (n = 5), and 32 μg/ml (n = 1). However, all isolates developed heteroresistant colonies, with increments in the MIC from 2 to 6 dilutions. Notably, 5 (16.1%) isolates of C. neoformans and 8 (33.3%) of C. gattii, grew up to 64 μg/ml of fluconazole, which is the MIC that defines resistance to this azole, and 1 (3,2%) isolate of C. neoformans and 4 (16.7%) of C. gattii grew up to 128 μg/ml of fluconazole. Currently, the ERG11 gene is being amplified for further sequencing. Conclusion: clinical isolates of C. neoformans and C. gattii that develop heteroresistance to fluconazole in high concentrations circulate in Colombia, which is important since this characteristic contributes to the relapse of cryptococcosis during therapy with this triazole.

P070 Antimicrobial peptides from the Coleoptera family Scarabaeidae against Candida and Cryptococcus pathogenic yeasts

 

Poster session 1, September 21, 2022, 12:30 PM - 1:30 PM

Objectives

Host defense peptides (HDP) are produced by a diversity of beetles. The aims of this work were (1) to find new promising peptides from the Coleoptera family Scarabaeidae with potential biomedical applications, (2) to modify physicochemical and structural characteristics of one of the most promissory peptides in order to improve its antimicrobial properties, and (3) to evaluate the in vitro activity of the HDPs against reference strains of pathogenic Candida and Cryptococcus yeasts.

Materials and Methods

From the Scarabaeidae family transcriptome, 14 promising HDPs were identified. Subsequently, we designed 19 new sequences from Act8 peptide modifying the net charge, hydrophobic angle, and the general composition of amino acids, among other properties, in order to improve the HDPs antifungal activity. The in vitro antifungal susceptibility of the 33 HDPs against C. albicans SC5314, C. krusei, ATCC 6558, C. parapsilosis ATCC 22019, C. glabrata ATCC 2001, C. tropicalis ATCC 750, C. neoformans H99, and C. gattii H0058-I-2029 isolates were evaluated by broth microdilution, with a concentration ranging from 0.19 to 50 μg/ml.

Results

All 14 peptides identified showed in vitro activity against C. krusei, C. parapsilosis, and C. glabrata. One peptide showed in vitro activity against C. albicans, 6 against C. tropicalis, 11 against C. neoformans and 13 against C. gattii. As well the 19 modified peptides showed in vitro activity against C. krusei, C. parapsilosis, C. tropicalis, C. neoformans, and C. gattii. A total of 15 modified peptides showed in vitro activity against C. albicans, and 3 against C. glabrata. MIC ranges per species and per peptide are shown in Table 1.

Conclusions

The HDPs herein analyzed showed a significant in vitro antifungal activity against six Candida and two Cryptococcus pathogenic species. Our findings encourage further work with in vivo experimental models in order to better understand the action mechanisms of these antimicrobial peptides. HDPs from different species are becoming a promising therapeutic alternative in the control of fungal infections.

P124 Cryptococcus neoformans-and Cryptococcus gattii-specific antibodies vary among children and adults with cryptococcosis and healthy from Colombia

 

Poster session 1, September 21, 2022, 12:30 PM - 1:30 PM

Background

Cryptococcus neoformans (Cn), predominantly, and Cryptococcus gattii (Cg) cause cryptococcosis, a life-threatening systemic mycosis of global distribution affecting mainly immunocompromised adults.

Objectives

This study aimed to determine total and specific antibodies against C. neoformans and C. gattii antigens in sera from patients with cryptococcosis and from healthy individuals from Colombia, which will help to elucidate sero-epidemiological variations in the incidence of the disease in the country.

Methods

Sera from child and adult patients with cryptococcosis (n = 109) and sera from healthy children and adults from Colombia (n = 119) were studied. Using ELISA, total and Cn- and Cg-specific levels of immunoglobulin (Ig)G, IgA, and IgM were determined in sera.

Results

Total IgG, IgA, and IgM levels were higher in HIV + compared with HIV− patients with cryptococcosis. Specific IgG, IgA, and IgM levels tended to be higher in cryptococcosis patients than in healthy controls and to be higher in adults than in children, with a positive correlation between antibody reactivity and age. All serum immunoglobulins were more reactive against Cn-proteins than Cg-proteins. Including all samples, a positive correlation between total and specific IgG, IgA, and IgM levels was found.

Conclusions

In cryptococcosis patients from Colombia, serum immunoglobulins levels differ depending on HIV status, as reported previously. However, this study shows for the first-time variations in immunoglobulin production among adults and children with cryptococcal disease and between Cn and Cg-protein antigens. The observation of differential antibody reactivity with cryptococcal proteins encourages further studies of the humoral immunity for host defense against cryptococcosis.

P002 Antifungal activity of antimicrobial synthetic peptides against Candida species of public health importance

Poster session 1, September 21, 2022, 12:30 PM - 1:30 PM

 

Background

Candidiasis is one of the most frequent opportunistic infections in immunosuppressed and/or hospitalized patients. In countries like Colombia, candidiasis is associated with a mortality rate of ∼ 46%. Growing pharmacological resistance of Candida spp., and the appearance of the emerging pathogen Candida auris, have turned candidiasis into a major public health problem. Different types of antimicrobial peptides have been investigated as a therapeutic alternative to control candidiasis effectively and safely.

Objective

This work aimed at evaluating the in vitro antifungal activity of three synthetic antimicrobial peptides (35 409, 1609, and 29 009) obtained from Plasmodium falciparum Rif1 protein against C. auris, C. albicans, C. glabrata, C. parapsilosis, C. krusei, and C. tropicalis, species with worldwide clinical importance.

Methods

The minimum inhibitory concentrations (MIC) of the three peptides against Candida species were determined by the plate microdilution method; the peptides’ effect on biofilm formation in C. auris and C. albicans species was also evaluated through the XTT metabolic activity assay. Additionally, the structural damages in C. auris and C. albicans caused by the action of the peptides were observed by transmission electron microscopy (TEM) and finally, the in vitro peptides’ cytotoxicity against L929 murine fibroblasts was verified.

Results

Our findings showed that the three peptides herein evaluated, displayed antifungal activity in both planktonic and sessile Candida cells. Likewise, the TEM evidenced morphological alterations induced by the peptides, both in the membrane and at the intracellular level of the yeasts. As well, total safety against the murine cell line L929 with 24 h of treatment was observed.

Conclusions

From these results, we conclude that the antimicrobial peptides 35 409, 1609, and 29 009 are potential therapeutic alternatives against the most important Candida species in Colombia and the world.

Cryptococcus neoformans- and Cryptococcus gattii-specific IgG, IgA and IgM differ among children and adults with and without cryptococcosis from Colombia

Cryptococcus neoformans (Cn) and Cryptococcus gattii (Cg) cause cryptococcosis, a life-threatening systemic mycosis of global distribution affecting mainly immunocompromised adults. Although a humoral response occurs during cryptococcosis, the role of antibody production against this mycosis is not fully understood. We aimed to determine total and specific antibodies against cryptococcal protein antigens in sera from people with and without diagnosis of cryptococcosis from Colombia. Using ELISA, total and specific levels of immunoglobulin (Ig)G, IgA and IgM were determined in sera from children and adults with (n = 109) and without (n = 119) cryptococcosis. Specific antibodies were those binding Cn- and Cg-protein antigens. In general, the mean of the total IgG production was higher in cryptococcosis patients than in controls (13 942.32 vs. 6459.91 µg/ml), while levels of IgA (488.13 vs. 1564.53 µg/ml) and IgM (775.69 vs. 1014.72 µg/ml) were higher in controls than in cryptococcosis patients (p ≤ 0.05). In patients with cryptococcosis, total IgG, IgA and IgM levels were higher in HIV + compared with HIV- (p ≤ 0.05). Specific antibodies tended to be higher in cryptococcosis patients than in controls and in adults than in children, with a positive correlation between antibody reactivity and age. All immunoglobulins were more reactive against Cn-proteins than Cg-proteins. Overall, a positive weak correlation between total and specific antibodies was found, although not always statistically significant. In patients with cryptococcosis from Colombia, the levels of immunoglobulins, total and specific, differ with respect to people without cryptococcosis. Variations in antibody production among adults and children with cryptococcosis and between Cn- and Cg-protein antigens were as well established. Our findings encourage further studies to determine the role of humoral immunity for host defence against cryptococcosis.

Molecular type distribution and fluconazole susceptibility of clinical Cryptococcus gattii isolates from South African laboratory-based surveillance, 2005–2013

As is the case globally, Cryptococcus gattii is a less frequent cause of cryptococcosis than Cryptococcus neoformans in South Africa. We performed multilocus sequence typing (MLST) and fluconazole susceptibility testing of 146 isolates randomly selected from 750 South African patients with C. gattii disease identified through enhanced laboratory surveillance, 2005 to 2013. The dominant molecular type was VGIV (101/146, 70%), followed by VGI (40/146, 27%), VGII (3/146, 2%) and VGIII (2/146, 1%). Among the 146 C. gattii isolates, 99 different sequence types (STs) were identified, with ST294 (14/146, 10%) and ST155 (10/146, 7%) being most commonly observed. The fluconazole MIC₅₀ and MIC₉₀ values of 105 (of 146) randomly selected C. gattii isolates were 4 μg/ml and 16 μg/ml, respectively. VGIV isolates had a lower MIC₅₀ value compared to non-VGIV isolates, but these values were within one double-dilution of each other. HIV-seropositive patients had a ten-fold increased adjusted odds of a VGIV infection compared to HIV-seronegative patients, though with small numbers (99/136; 73% vs. 2/10; 20%), the confidence interval (CI) was wide (95% CI: 1.93–55.31, p = 0.006). Whole genome phylogeny of 98 isolates of South Africa’s most prevalent molecular type, VGIV, identified that this molecular type is highly diverse, with two interesting clusters of ten and six closely related isolates being identified, respectively. One of these clusters consisted only of patients from the Mpumalanga Province in South Africa, suggesting a similar environmental source. This study contributed new insights into the global population structure of this important human pathogen.

Cryptococcus is the most common cause of meningitis among adults in South Africa. Most human disease is caused by the members of two species complexes within the genus, Cryptococcus neoformans and Cryptococcus gattii. The environmental range of these species complexes, both found in soil, overlaps in southern Africa though C. gattii is a less common human pathogen. C. gattii is divided into six molecular types: VGI, VGII, VGIII, VGIV, VGV and VGVI. In earlier molecular epidemiology studies including relatively few isolates, most southern African isolates were confirmed as molecular type VGIV. We aimed to determine the molecular diversity of C. gattii in South Africa by genotyping patient isolates obtained through laboratory surveillance, 2005–2013. We confirmed that VGIV was the dominant molecular type and that HIV-seropositive patients were more likely to be infected with VGIV compared to those HIV-seronegative. Analysis of the genomes of South African VGIV isolates revealed that they spanned the whole VGIV clade and confirmed that most isolates did not cluster specifically. However, we observed two interesting clusters of closely related isolates, consisting of patients from three neighbouring provinces in South Africa, suggesting a similar environmental source. Further studies of clinical and environmental African C. gattii isolates are needed to gain a better understanding of this pathogen.

Multilocus Sequence Typing Reveals Extensive Genetic Diversity of the Emerging Fungal Pathogen Scedosporium aurantiacum

Scedosporium spp. are the second most prevalent filamentous fungi after Aspergillus spp. recovered from cystic fibrosis (CF) patients in various regions of the world. Although invasive infection is uncommon prior to lung transplantation, fungal colonization may be a risk factor for invasive disease with attendant high mortality post-transplantation. Abundant in the environment, Scedosporium aurantiacum has emerged as an important fungal pathogen in a range of clinical settings. To investigate the population genetic structure of S. aurantiacum, a MultiLocus Sequence Typing (MLST) scheme was developed, screening 24 genetic loci for polymorphisms on a tester strain set. The six most polymorphic loci were selected to form the S. aurantiacum MLST scheme: actin (ACT), calmodulin (CAL), elongation factor-1α (EF1α), RNA polymerase subunit II (RPB2), manganese superoxide dismutase (SOD2), and β-tubulin (TUB). Among 188 global clinical, veterinary, and environmental strains, 5 to 18 variable sites per locus were revealed, resulting in 8 to 23 alleles per locus. MLST analysis observed a markedly high genetic diversity, reflected by 159 unique sequence types. Network analysis revealed a separation between Australian and non-Australian strains. Phylogenetic analysis showed two major clusters, indicating correlation with geographic origin. Linkage disequilibrium analysis revealed evidence of recombination. There was no clustering according to the source of the strains: clinical, veterinary, or environmental. The high diversity, especially amongst the Australian strains, suggests that S. aurantiacum may have originated within the Australian continent and was subsequently dispersed to other regions, as shown by the close phylogenetic relationships between some of the Australian sequence types and those found in other parts of the world. The MLST data are accessible at http://mlst.mycologylab.org. This is a joined publication of the ISHAM/ECMM working groups on “Scedosporium/Pseudallescheria Infections” and “Fungal Respiratory Infections in Cystic Fibrosis”.

Identification of Disease-Associated Cryptococcal Proteins Reactive With Serum IgG From Cryptococcal Meningitis Patients

Cryptococcus neoformans, an opportunistic fungal pathogen ubiquitously present in the environment, causes cryptococcal meningitis (CM) mainly in immunocompromised patients, such as AIDS patients. We aimed to identify disease-associated cryptococcal protein antigens targeted by the human humoral immune response. Therefore, we used sera from Colombian CM patients, with or without HIV infection, and from healthy individuals living in the same region. Serological analysis revealed increased titers of anti-cryptococcal IgG in HIV-negative CM patients, but not HIV-positive CM patients, compared to healthy controls. In contrast, titers of anti-cryptococcal IgM were not affected by CM. Furthermore, we detected pre-existing IgG and IgM antibodies even in sera from healthy individuals. The observed induction of anti-cryptococcal IgG but not IgM during CM was supported by analysis of sera from C. neoformans-infected mice. Stronger increase in IgG was found in wild type mice with high lung fungal burden compared to IL-4Rα-deficient mice showing low lung fungal burden. To identify the proteins targeted by human anti-cryptococcal IgG antibodies, we applied a quantitative 2D immunoproteome approach identifying cryptococcal protein spots preferentially recognized by sera from CM patients or healthy individuals followed by mass spectrometry analysis. Twenty-three cryptococcal proteins were recombinantly expressed and confirmed to be immunoreactive with human sera. Fourteen of them were newly described as immunoreactive proteins. Twelve proteins were classified as disease-associated antigens, based on significantly stronger immunoreactivity with sera from CM patients compared to healthy individuals. The proteins identified in our screen significantly expand the pool of cryptococcal proteins with potential for (i) development of novel anti-cryptococcal agents based on implications in cryptococcal virulence or survival, or (ii) development of an anti-cryptococcal vaccine, as several candidates lack homology to human proteins and are localized extracellularly. Furthermore, this study defines pre-existing anti-cryptococcal immunoreactivity in healthy individuals at a molecular level, identifying target antigens recognized by sera from healthy control persons.

Antifungal susceptibility of clinical Cryptococcus gattii isolates from Colombia varies among molecular types

Cryptococcosis by Cryptococcus gattii is endemic in Colombia, affecting mostly immunocompetent hosts. Since antifungal susceptibility differs between molecular types of cryptococcal isolates, as reported elsewhere, the aim of this study was to determine if 42 Colombian clinical isolates, VGI, VGII and VGIII, differ in the susceptibility to commonly used antifungals, using Sensititre plates. Among the molecular types, six non-wild type isolates to fluconazole, voriconazole and 5-flucytosine, were identified. Besides, VGI and VGII were less susceptible to 5-flucytosine and azoles, respectively, than other molecular types. These findings support the applicability of practicing susceptibility testing, which could better guide treatment in cryptococcosis.

Genotype, Antifungal Susceptibility, and Virulence of Clinical South African Cryptococcus neoformans Strains from National Surveillance, 2005-2009

In South Africa, Cryptococcus neoformans is the most common cause of adult meningitis. We performed multi locus sequence typing and fluconazole susceptibility testing of clinical C. neoformans isolates collected from 251 South African patients with cryptococcosis through national surveillance from 2005 to 2009. We examined the association between clinical characteristics of patients and genotype, and the effect of genotype on in-hospital mortality. We performed whole genome phylogenetic analysis of fifteen C. neoformans isolates with the molecular type VNB and tested their virulence in a Galleria mellonella model. Most isolates had the molecular type VNI (206/251, 82%), followed by VNII (25/251, 10%), VNB (15/251, 6%), and VNIV (5/251, 2%); 67 sequence types were identified. There were no differences in fluconazole minimum inhibitory concentration (MIC) values among molecular types and the majority of strains had low MIC values (MIC₅₀ of 1 µg/mL and MIC₉₀ of 4 µg/mL). Males were almost twice as likely of being infected with a non-VNI genotype (adjusted odds ratio [OR]: 1.65, 95% confidence interval [CI]: 0.25–10.99; p = 0.61). Compared to patients infected with a VNI genotype, those with a non-VNI genotype had a 50% reduced adjusted odds of dying in hospital (95% CI: 0.03–7.57; p = 0.62). However, for both these analyses, our estimates had wide confidence intervals spanning 1 with large p-values. Fifteen VNB strains were not as virulent in a G. mellonella larval model as the H99 reference strain. A majority of these VNB strains belonged to the VNBII clade and were very closely related by phylogenetic analysis.

Cryptococcus neoformans and Cryptococcus gattii Species Complexes in Latin America: A Map of Molecular Types, Genotypic Diversity, and Antifungal Susceptibility as Reported by the Latin American Cryptococcal Study Group

Cryptococcosis, a potentially fatal mycosis, is caused by members of the Cryptococcus neoformans and Cryptococcus gattii species complexes. In Latin America, cryptococcal meningitis is still an important health threat with a significant clinical burden. Analysis of publicly available molecular data from 5686 clinical, environmental, and veterinary cryptococcal isolates from member countries of the Latin American Cryptococcal Study Group showed that, as worldwide, C. neoformans molecular type VNI is the most common cause of cryptococcosis (76.01%) in HIV-infected people, followed by C. gattii molecular type VGII (12.37%), affecting mostly otherwise healthy hosts. These two molecular types also predominate in the environment (68.60% for VNI and 20.70% for VGII). Among the scarce number of veterinary cases, VGII is the predominant molecular type (73.68%). Multilocus sequence typing analysis showed that, in Latin America, the C. neoformans population is less diverse than the C. gattii population (D of 0.7104 vs. 0.9755). Analysis of antifungal susceptibility data showed the presence of non-wild-type VNI, VGI, VGII, and VGIII isolates in the region. Overall, the data presented herein summarize the progress that has been made towards the molecular epidemiology of cryptococcal isolates in Latin America, contributing to the characterization of the genetic diversity and antifungal susceptibility of these globally spreading pathogenic yeasts.

Invasive fungal disease in humans: are we aware of the real impact?

Despite the medical advances and interventions to improve the quality of life of those in intensive care, people with cancer or severely immunocompromised or other susceptible hosts, invasive fungal diseases (IFD) remain severe and underappreciated causes of illness and death worldwide. Therefore, IFD continue to be a public health threat and a major hindrance to the success of otherwise life-saving treatments and procedures. Globally, hundreds of thousands of people are affected every year with Candida albicans, Aspergillus fumigatus, Cryptococcus neoformans, Pneumocystis jirovecii, endemic dimorphic fungi and Mucormycetes, the most common fungal species causing invasive diseases in humans. These infections result in morbidity and mortality rates that are unacceptable and represent a considerable socioeconomic burden. Raising the general awareness of the significance and impact of IFD in human health, in both the hospital and the community, is hence critical to understand the scale of the problem and to raise interest to help fighting these devastating diseases.

Rearing and Maintenance of Galleria mellonella and Its Application to Study Fungal Virulence

Galleria mellonella larvae have been widely used as alternative non-mammalian models for the study of fungal virulence and pathogenesis. The larvae can be acquired in small volumes from worm farms, pet stores, or other independent suppliers commonly found in the United States and parts of Europe. However, in countries with no or limited commercial availability, the process of shipping these larvae can cause them stress, resulting in decreased or altered immunity. Furthermore, the conditions used to rear these larvae including diet, humidity, temperature, and maintenance procedures vary among the suppliers. Variation in these factors can affect the response of G. mellonella larvae to infection, thereby decreasing the reproducibility of fungal virulence experiments. There is a critical need for standardized procedures and incubation conditions for rearing G. mellonella to produce quality, unstressed larvae with the least genetic variability. In order to standardize these procedures, cost-effective protocols for the propagation and maintenance of G. mellonella larvae using an artificial diet, which has been successfully used in our own laboratory, requiring minimal equipment and expertise, are herein described. Examples for the application of this model in fungal pathogenicity and gene knockout studies as feasible alternatives for traditionally used animal models are also provided.

Fatal fungaemia due to Cryptococcus albidus in an elderly diabetic woman presenting with pleural effusion

This is a fatal case of fungaemia due to Cryptococcus albidus in an elderly woman with type 2 diabetes mellitus who presented pleural effusion as the only clinical presentation. Not only infections of the pleura are uncommon presentations of pulmonary cryptococcosis, but these infections due to non-C. neoformans species are extremely rare. This report places C. albidus on the growing number of disseminated mycosis-causing agents in diabetic patients.

Indoor Dust as a Source of Virulent Strains of the Agents of Cryptococcosis in the Rio Negro Micro-Region of the Brazilian Amazon

Cryptococcosis, a potentially fatal mycosis in humans, is acquired via exposure to exogenous environmental sources. This study aimed to investigate the frequency, genetic diversity, and virulence of cryptococcal strains isolated from indoor dust in the Rio Negro micro-region of the Brazilian Amazon. A total of 8.9% of the studied houses were positive, recovering nine Cryptococcus neoformans VNI and 16 C. gattii VGII isolates, revealing an endemic pattern in domestic microenvironments. The International Society for Human and Animal Mycology (ISHAM) consensus multilocus sequence typing (MLST) scheme for the C. neoformans/C. gattii species complexes identified two sequence types (STs), ST93 and ST5, amongst C. neoformans isolates and six STs amongst C. gattii isolates, including the Vancouver Island Outbreak ST7 (VGIIa) and ST20 (VGIIb), the Australian ST5, and ST264, ST268 and ST445, being unique to the studied region. Virulence studies in the Galleria mellonella model showed that five C.gattii strains and one C. neoformans strain showed a similar pathogenic potential to the highly virulent Vancouver Island outbreak strain CDR265 (VGIIa). The findings of this study indicate that humans can be exposed to the agents of cryptococcosis via house dust, forming the basis for future studies to analyze the impact of early and continuous exposure to indoor dust on the development of subclinical or clinical infections.

Clonal Dispersal of Cryptococcus gattii VGII in an Endemic Region of Cryptococcosis in Colombia

This study characterized the genotype and phenotype of Cryptococcus gattii VGII isolates from Cucuta, an endemic region of cryptococcal disease in Colombia, and compared these traits with those from representative isolates from the Vancouver Island outbreak (VGIIa and VGIIb). Genetic diversity was assessed by multilocus sequence typing (MLST) analysis. Phenotypic characteristics, including growth capacity under different temperature and humidity conditions, macroscopic and microscopic morphology, phenotypic switching, mating type, and activity of extracellular enzymes were studied. Virulence was studied in vivo in a mouse model. MLST analysis showed that the isolates from Cucuta were highly clonal, with ST25 being the most common genotype. Phenotypically, isolates from Cucuta showed large cell and capsular sizes, and shared phenotypic traits and enzymatic activities among them. The mating type a prevailed among the isolates, which were fertile and of considerable virulence in the animal model. This study highlights the need for a continuous surveillance of C. gattii in Colombia, especially in endemic areas like Cucuta, where the highest number of cryptococcosis cases due to this species is reported. This will allow the early detection of potentially highly virulent strains that spread clonally, and can help prevent the occurrence of outbreaks in Colombia and elsewhere.

The status of cryptococcosis in Latin America

Cryptococcosis is a life-threatening fungal infection caused by the encapsulated yeasts Cryptococcus neoformans and C. gattii, acquired from the environment. In Latin America, as occurring worldwide, C. neoformans causes more than 90% of the cases of cryptococcosis, affecting predominantly patients with HIV, while C. gattii generally affects otherwise healthy individuals. In this region, cryptococcal meningitis is the most common presentation, with amphotericin B and fluconazole being the antifungal drugs of choice. Avian droppings are the predominant environmental reservoir of C. neoformans, while C. gattii is associated with several arboreal species. Importantly, C. gattii has a high prevalence in Latin America and has been proposed to be the likely origin of some C. gattii populations in North America. Thus, in the recent years, significant progress has been made with the study of the basic biology and laboratory identification of cryptococcal strains, in understanding their ecology, population genetics, host-pathogen interactions, and the clinical epidemiology of this important mycosis in Latin America.

Advances in the understanding of the Cryptococcus neoformans and C. gattii species complexes and cryptococcosis

The rising incidence of cryptococcosis, a potentially fatal fungal infection affecting both immunocompromised and immunocompetent humans and animals, and the emergence of disease outbreaks, has increased the need for more in-depth studies and constant vigilance of its two etiological agents, the cosmopolitan and well known Cryptococcus neoformans and its sibling species C. gattii. As a result, a global scientific network has established formal links between institutions to gain better insights into Cryptococcus and cryptococcosis, enabling collaborations amongst researchers with different backgrounds, perspectives and skills. Interdisciplinary projects include: (1) the study of the ecology and geographical distribution of the agents of cryptococcosis; (2) the application of new alternative methodologies for the rapid and accurate identification of the two sibling species and major molecular types/possible cryptic species (VNI-VNIV and VGI-VGIV); (3) the use of different animal models of infection to assess cryptococcal pathogenesis and virulence factors; and (4) population genetics studies directed towards the discovery of virulence/tissue tropism associated genetic signatures. These studies enrich the knowledge and understanding of the epidemiology of this mycosis and help to better comprehend fungal virulence, genetics, pathogenesis, antifungal susceptibility, as well as investigating the regional and global spread, to improve treatment options of the disease caused by these important emerging pathogenic yeasts.

MLST and Whole-Genome-Based Population Analysis of Cryptococcus gattii VGIII Links Clinical, Veterinary and Environmental Strains, and Reveals Divergent Serotype Specific Sub-populations and Distant Ancestors

The emerging pathogen Cryptococcus gattii causes life-threatening disease in immunocompetent and immunocompromised hosts. Of the four major molecular types (VGI-VGIV), the molecular type VGIII has recently emerged as cause of disease in otherwise healthy individuals, prompting a need to investigate its population genetic structure to understand if there are potential genotype-dependent characteristics in its epidemiology, environmental niche(s), host range and clinical features of disease. Multilocus sequence typing (MLST) of 122 clinical, environmental and veterinary C. gattii VGIII isolates from Australia, Colombia, Guatemala, Mexico, New Zealand, Paraguay, USA and Venezuela, and whole genome sequencing (WGS) of 60 isolates representing all established MLST types identified four divergent sub-populations. The majority of the isolates belong to two main clades, corresponding either to serotype B or C, indicating an ongoing species evolution. Both major clades included clinical, environmental and veterinary isolates. The C. gattii VGIII population was genetically highly diverse, with minor differences between countries, isolation source, serotype and mating type. Little to no recombination was found between the two major groups, serotype B and C, at the whole and mitochondrial genome level. C. gattii VGIII is widespread in the Americas, with sporadic cases occurring elsewhere, WGS revealed Mexico and USA as a likely origin of the serotype B VGIII population and Colombia as a possible origin of the serotype C VGIII population. Serotype B isolates are more virulent than serotype C isolates in a murine model of infection, causing predominantly pulmonary cryptococcosis. No specific link between genotype and virulence was observed. Antifungal susceptibility testing against six antifungal drugs revealed that serotype B isolates are more susceptible to azoles than serotype C isolates, highlighting the importance of strain typing to guide effective treatment to improve the disease outcome.

Cryptococcus gattii, which is classically divided into four major molecular types (VGI-VGIV), and two serotypes B and C, is the second most important cause of cryptococcosis. The rising incidence of human and animal cryptococcosis cases caused by molecular type VGIII highlights the need for increased vigilance. In this study, we characterized a large set of C. gattii VGIII isolates. Genetic analysis revealed four diverging sub-populations, which were primarily associated with serotype B or C, and very likely originated from endemic regions in Colombia, Mexico and the USA. Differences in virulence and antifungal susceptibility between serotypes may result in different disease outcomes since serotype B isolates were more virulent in mice than serotype C isolates, but serotype C isolates were less susceptible to azoles, the primary treatment for uncomplicated cryptococcosis. Identification of cryptococcal serotype and molecular type in clinical practice has the potential to guide treatment regimens and hence reduce morbidity and mortality in both sporadic cases and those associated with outbreaks. Our study significantly contributes to the understanding of the epidemiology, genetics and pathogenesis of Cryptococcus and cryptococcosis.

Pathogenic diversity amongst serotype C VGIII and VGIV Cryptococcus gattii isolates

Cryptococcus gattii is one of the causative agents of human cryptococcosis. Highly virulent strains of serotype B C. gattii have been studied in detail, but little information is available on the pathogenic properties of serotype C isolates. In this study, we analyzed pathogenic determinants in three serotype C C. gattii isolates (106.97, ATCC 24066 and WM 779). Isolate ATCC 24066 (molecular type VGIII) differed from isolates WM 779 and 106.97 (both VGIV) in capsule dimensions, expression of CAP genes, chitooligomer distribution, and induction of host chitinase activity. Isolate WM 779 was more efficient than the others in producing pigments and all three isolates had distinct patterns of reactivity with antibodies to glucuronoxylomannan. This great phenotypic diversity reflected in differential pathogenicity. VGIV isolates WM 779 and 106.97 were similar in their ability to cause lethality and produced higher pulmonary fungal burden in a murine model of cryptococcosis, while isolate ATCC 24066 (VGIII) was unable to reach the brain and caused reduced lethality in intranasally infected mice. These results demonstrate a high diversity in the pathogenic potential of isolates of C. gattii belonging to the molecular types VGIII and VGIV.

Retrospective study of the epidemiology and clinical manifestations of Cryptococcus gattii infections in Colombia from 1997-2011

BACKGROUND

Cryptococcosis due to Cryptococcus gattii is endemic in various parts of the world, affecting mostly immunocompetent patients. A national surveillance study of cryptococcosis, including demographical, clinical and microbiological data, has been ongoing since 1997 in Colombia, to provide insights into the epidemiology of this mycosis.

METHODOLOGY/PRINCIPAL FINDINGS

From 1,209 surveys analyzed between 1997-2011, 45 cases caused by C. gattii were reported (prevalence 3.7%; annual incidence 0.07 cases/million inhabitants/year). Norte de Santander had the highest incidence (0.81 cases/million/year), representing 33.3% of all cases. The male: female ratio was 3.3∶1. Mean age at diagnosis was 41±16 years. No specific risk factors were identified in 91.1% of patients. HIV infection was reported in 6.7% of patients, autoimmune disease and steroids use in 2.2%. Clinical features included headache (80.5%), nausea/vomiting (56.1%) and neurological derangements (48.8%). Chest radiographs were taken in 21 (46.7%) cases, with abnormal findings in 7 (33.3%). Cranial CT scans were obtained in 15 (33.3%) cases, with abnormalities detected in 10 (66.7%). Treatment was well documented in 30 cases, with most receiving amphotericin B. Direct sample examination was positive in 97.7% cases. Antigen detection was positive for all CSF specimens and for 75% of serum samples. C. gattii was recovered from CSF (93.3%) and respiratory specimens (6.6%). Serotype was determined in 42 isolates; 36 isolates were serotype B (85.7%), while 6 were C (14.3%). The breakdowns of molecular types were VGII (55.6%), VGIII (31.1%) and VGI (13.3%). Among 44 strains, 16 MLST sequence types (ST) were identified, 11 of them newly reported.

CONCLUSIONS/SIGNIFICANCE

The results of this passive surveillance study demonstrate that cryptococcosis caused by C. gattii has a low prevalence in Colombia, with the exception of Norte de Santander. The predominance of molecular type VGII is of concern considering its association with high virulence and the potential to evolve into outbreaks.

Galleria mellonella model identifies highly virulent strains among all major molecular types of Cryptococcus gattii

Cryptococcosis is mainly caused by Cryptococcus neoformans. However, the number of cases due to C. gattii is increasing, affecting mainly immunocompetent hosts. C. gattii is divided into four major molecular types, VGI to VGIV, which differ in their host range, epidemiology, antifungal susceptibility and geographic distribution. Besides studies on the Vancouver Island outbreak strains, which showed that the subtype VGIIa is highly virulent compared to the subtype VGIIb, little is known about the virulence of the other major molecular types. To elucidate the virulence potential of the major molecular types of C. gattii, Galleria mellonella larvae were inoculated with ten globally selected strains per molecular type. Survival rates were recorded and known virulence factors were studied. One VGII, one VGIII and one VGIV strain were more virulent (p <0.05) than the highly virulent Vancouver Island outbreak strain VGIIa (CDCR265), 11 (four VGI, two VGII, four VGIII and one VGIV) had similar virulence (p >0.05), 21 (five VGI, five VGII, four VGIII and seven VGIV) were less virulent (p <0.05) while one strain of each molecular type were avirulent. Cell and capsule size of all strains increased markedly during larvae infection (p <0.001). No differences in growth rate at 37°C were observed. Melanin synthesis was directly related with the level of virulence: more virulent strains produced more melanin than less virulent strains (p <0.05). The results indicate that all C. gattii major molecular types exhibit a range of virulence, with some strains having the potential to be more virulent. The study highlights the necessity to further investigate the genetic background of more and less virulent strains in order to recognize critical features, other than the known virulence factors (capsule, melanin and growth at mammalian body temperature), that maybe crucial for the development and progression of cryptococcosis.

MALDI-TOF MS for the identification of veterinary non-C. neoformans-C. gattii Cryptococcus spp. isolates from Italy

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) offers an effective alternative to phenotypic and molecular methods for the rapid identification of microorganisms. Our aim in this study was to create an in-house library for a set of strains of nine uncommonly reported human and animal cryptococcal species, including Cryptococcus adeliensis, C. albidosimilis, C. albidus, C. aureus, C. carnescens, C. laurentii, C. magnus, C. victoriae and C. uniguttulatus, and to use this library to make timely and correct identifications using MALDI-TOF MS for use in routine laboratory diagnostics. Protein extracts obtained via the formic acid extraction method of 62 veterinary non-C. neoformans-C. gattii cryptococcal isolates were studied. The obtained mass spectra correctly grouped all 62 studied isolates according to species identification previously obtained by internal transcribe spacer sequence analysis. The in-house database was than exported and successfully uploaded to the Microflex LT (Maldi Biotyper; Bruker Daltonics) instrument at a different diagnostic laboratory in Italy. Scores >2.7 obtained from isolates reanalyzed in the latter laboratory supported the high reproducibility of the method. The possibility of creating and transferring an in-house library adds to the usefulness MALDI-TOF MS an important tool for the rapid and inexpensive identification of pathogenic and saprophytic fungi as required for differential diagnosis of human and animal mycoses.

Identification of the major molecular types of Cryptococcus neoformans and C. gattii by Hyperbranched rolling circle amplification

The agents of cryptococcosis C. neoformans and C. gattii are important agents of meningoencephalitis in immunocompromised and immunocompetent hosts, respectively. They are grouped into eight major molecular types, VNI-VNIV for C. neoformans and VGI-VGIV for C. gattii. These major molecular types differ in their host range, epidemiology, antifungal susceptibility and geographic distribution. To enable a rapid identification of the major molecular types and potential hybrids within the two species specific probes based on the PLB1 gene in combination with hyperbranched rolling circle amplification (HRCA) were developed. HRCA was applied to 76 cryptococcal strains, 10 strains each representing the 7 haploid major molecular types, 4 VNIII hybrid strains and 2 inter-species hybrid strains. All strains were correctly identified to the major molecular type and or hybrid type using HRCA alone. To increase the sensitivity a semi-nested PCR step was developed, which will enable the identification of the molecular types/hybrids directly from clinical samples, harboring a low copy number of DNA (40 copies). Thus, HRCA based on the PLB1 locus alone and in combination with a semi-nested PCR showed to be a specific and sensitive methodology, with a great potential to be used on clinical specimens for the direct diagnosis of the agents of cryptococcosis, including hybrid strains, enabling a rapid and patient tailored treatment choice of this disease.

Molecular epidemiology reveals genetic diversity amongst isolates of the Cryptococcus neoformans/C. gattii species complex in Thailand

To gain a more detailed picture of cryptococcosis in Thailand, a retrospective study of 498 C. neoformans and C. gattii isolates has been conducted. Among these, 386, 83 and 29 strains were from clinical, environmental and veterinary sources, respectively. A total of 485 C. neoformans and 13 C. gattii strains were studied. The majority of the strains (68.9%) were isolated from males (mean age of 37.97 years), 88.5% of C. neoformans and only 37.5% of C. gattii strains were from HIV patients. URA5-RFLP and/or M13 PCR-fingerprinting analysis revealed that the majority of the isolates were C. neoformans molecular type VNI regardless of their sources (94.8%; 94.6% of the clinical, 98.8% of the environmental and 86.2% of the veterinary isolates). In addition, the molecular types VNII (2.4%; 66.7% of the clinical and 33.3% of the veterinary isolates), VNIV (0.2%; 100% environmental isolate), VGI (0.2%; 100% clinical isolate) and VGII (2.4%; 100% clinical isolates) were found less frequently. Multilocus Sequence Type (MLST) analysis using the ISHAM consensus MLST scheme for the C. neoformans/C. gattii species complex identified a total of 20 sequence types (ST) in Thailand combining current and previous data. The Thai isolates are an integrated part of the global cryptococcal population genetic structure, with ST30 for C. gattii and ST82, ST83, ST137, ST141, ST172 and ST173 for C. neoformans being unique to Thailand. Most of the C. gattii isolates were ST7 = VGIIb, which is identical to the less virulent minor Vancouver island outbreak genotype, indicating Thailand as a stepping stone in the global spread of this outbreak strain. The current study revealed a greater genetic diversity and a wider range of major molecular types being present amongst Thai cryptococcal isolates than previously reported.

MALDI-TOF MS enables the rapid identification of the major molecular types within the Cryptococcus neoformans/C. gattii species complex

Background

The Cryptococcus neoformans/C. gattii species complex comprises two sibling species that are divided into eight major molecular types, C. neoformans VNI to VNIV and C. gattii VGI to VGIV. These genotypes differ in host range, epidemiology, virulence, antifungal susceptibility and geographic distribution. The currently used phenotypic and molecular identification methods for the species/molecular types are time consuming and expensive. As Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF MS) offers an effective alternative for the rapid identification of microorganisms, the objective of this study was to examine its potential for the identification of C. neoformans and C. gattii strains at the intra- and inter-species level.

Methodology

Protein extracts obtained via the formic acid extraction method of 164 C. neoformans/C. gattii isolates, including four inter-species hybrids, were studied.

Results

The obtained mass spectra correctly identified 100% of all studied isolates, grouped each isolate according to the currently recognized species, C. neoformans and C. gattii, and detected potential hybrids. In addition, all isolates were clearly separated according to their major molecular type, generating greater spectral differences among the C. neoformans molecular types than the C. gattii molecular types, most likely reflecting a closer phylogenetic relationship between the latter. The number of colonies used and the incubation length did not affect the results. No spectra were obtained from intact yeast cells. An extended validated spectral library containing spectra of all eight major molecular types was established.

Conclusions

MALDI-TOF MS is a rapid identification tool for the correct recognition of the two currently recognized human pathogenic Cryptococcus species and offers a simple method for the separation of the eight major molecular types and the detection of hybrid strains within this species complex in the clinical laboratory. The obtained mass spectra provide further evidence that the major molecular types warrant variety or even species status.

First environmental isolation of Cryptococcus gattii serotype B, from Cúcuta, Colombia

INTRODUCTION

In Cúcuta, Cryptococcus gattii serotype B is commonly recovered from immunocompetent patients with cryptococcosis, but it has not been recovered from the environment in spite of its high incidence which is 77% out of reported cases.

OBJECTIVE

The aim of this work was to carry out an extensive environmental sampling in Cúcuta, in an attempt to isolate C. gattii serotype B and to expand our knowledge about the ecology and epidemiology of this important yeast.

MATERIALS AND METHODS

Samples associated with 3,634 trees from 40 zones of Cúcuta were collected and processed with 28 samples collected near the houses of four patients with cryptococcosis caused by C. gattii serotype B. The serotype of the recovered isolates was done using multiplex PCR, molecular patterns were determined by RFLP of the URA5 gene and mating type was determined using the primers MfαU, MfαL, MFa2U and MFa2L.

RESULTS

In total, 4,389 samples were processed and one isolate of C. gattii serotype B (VGI/a), two isolates of C. gattii serotype C (VGIII/α) and three isolates of C. neoformans var. grubii, serotype A (VNI/α), were recovered. The density of the recovered isolates varied from 50 to 350 cfu/g of soil.

CONCLUSIONS

This is the first report on the environmental isolation of C. gattii serotype B from Cúcuta. However, because of the low rate of recovery of isolates from soil only, the environmental niche of C. gattii has not been established and further environmental studies in Cúcuta are necessary, owing that this serotype is not only causing cryptococcosis but also has shown a higher virulence after the Vancouver outbreak.

Fatal disseminated Cryptococcus gattii infection in New Mexico

We report a case of fatal disseminated infection with Cryptococcus gattii in a patient from New Mexico. The patient had no history of recent travel to known C. gattii-endemic areas. Multilocus sequence typing revealed that the isolate belonged to the major molecular type VGIII. Virulence studies in a mouse pulmonary model of infection demonstrated that the strain was less virulent than other C. gattii strains. This represents the first documented case of C. gattii likely acquired in New Mexico.

Circulation of Streptococcus pneumoniae clone Colombia 5 ST289 in nine Latin American countries

OBJECTIVE

To determine genetic relatedness of clone Colombia(5) ST289 with invasive Streptococcus pneumoniae serotype 5 isolates recovered in nine Latin American countries.

METHODS

Forty-four invasive S. pneumoniae serotype 5 isolates recovered from children under 5 years of age in Bolivia, Chile, Dominican Republic, Ecuador, Nicaragua, Panama, Paraguay, Peru, and Venezuela were studied. Pulsed-field gel electrophoresis patterns of DNA treated with SmaI restriction enzyme were classified using Tenover's criteria and analyzed with the Fingerprinting II program to determine their genetic relatedness with the Colombian clone.

RESULTS

All isolates had a genetic similarity of 78.5% or more with the Colombian clone. Thirteen electrophoretic subtypes derived of pattern A were identified, and five of them (A5, A6, A8, A13, A27) comprised 61.4% of the isolates.

CONCLUSIONS

Clone Colombia(5) ST289 is disseminated in Latin America. This is important because S. pneumoniae serotype 5 frequently causes invasive disease in the region and is associated with trimethoprim-sulfamethoxazole resistance.

[Molecular characterization of Colombian invasive serotype 5 Streptococcus pneumoniae isolates recovered between 1994 and 2004]

BACKGROUND

Streptococcus pneumoniae serotype 5 is an important cause of invasive disease in Colombia where the circulation of the clone Colombia5-19, penicillin susceptible but tetracycline and chloramphenicol resistant, has been demonstrated.

OBJECTIVE

To establish the genetic relatedness among Colombian invasive S. pneumoniae serotype 5 isolates, recovered between 1994 and 2004, and the clone Colombia(5)-19.

MATERIALS AND METHODS

Eighty three isolates with penicillin, vancomycin, ceftriaxone, erythromycin, trimethoprim-sulfametoxazole, chloramphenicol and tetracycline susceptibility patterns were studied. Of these isolates, 29 were recovered from children less than 5 years of age. DNA restriction patterns of all isolates were determined for pulsed field gel electrophoresis, using the Smal enzyme. Genetic similarity among isolates and the clone Colombia(5)-19 was established according to Tenover's criteria and the Fingerprintingä II program.

RESULTS

All isolates were related with the Colombia(5)-19 clone and belonged to the electrophoretic pattern A, of which 17 subtypes were derived. Most of the isolates belonged to patterns A (38,6%), A8 (21,7%) and A5 (12%), the other 23 isolates belonged to 15 electrophoretic patterns. Thirty -four isolates resistant both to tetracycline and chloramphenicol were related with electrophoretic patterns A (n = 32), A16 (n = 1) and A28 (n = 1), which have a band of 340 Kb in common with the clone.

CONCLUSION

These results showed the continuing circulation of S pneumoniae serotype 5 isolates in the country, and which are genetically related with the clone Colombia(5)-19.